共查询到20条相似文献,搜索用时 937 毫秒
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变重量光正交码用于光码分多址通信系统以满足不同服务质量用户需求.给出当u≥5为素数时,最优(16u,{3,5},1,{2/3,1/3))交重量光正交码的具体构造.同时证明了当u≥5为素数时,存在一个最优(25u,{3,4,5},1,{1/4,2/4,1/4})变重量光正交码.这将改进变重量光正交码的存在性结果. 相似文献
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在光纤码分多址(OCDMA)系统中,变重量光正交码被广泛使用,以满足多种服务质量的需求.利用分圆类和斜starter给出了直接构造方法,借助有关循环差阵的递归构造方法,从而构造了两类循环填充设计.通过建立循环填充设计与变重量光正交码之间的联系,证明了当Q∈{{2/3,1/3},{3/4,1/4}}时,最优(v,{3,4},1,Q)-光正交码存在的无穷类. 相似文献
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利用不同的序列作为波长跳频序列和时间扩频序列可以构造出不同的二维光正交码在众多文献中已有所报道.在经过正交拉丁方(OLS)与跳频序列的相关性研究之后.做了以下主要工作:首先,将正交拉丁方(OLS)序列作为波长跳频序列,结合一维时间扩频序列(OOC),构造了一种OLS/OOC二维光正交码.然后,本文对构造的OLS/OOC进行了多种性能仿真和分析.相对于PC/OOC、OCFHC/OOC等二维光正交码而言,OLS/OOC的波长数并不局限于素数,更能充分利用MWOCDMA系统中的有效波长数.仿真和分析表明:码字具有很好的相关性能,码字容量直逼理论极限,为一种渐近最优二维光正交码. 相似文献
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给出一种构造环F2+uF2+…+ukF2上任意偶数长度的自正交和自对偶码的方法.定义了环F2+uF2+…+ukF2的每个元素的Euclidean重量并且证明了环F2+uF2+…+ukF2上的自对偶码是Euclidean重量为2k+2倍数的TypeⅡ码. 相似文献
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Optical orthogonal code (OOC) has good correlation properties. It has many important applications in a fiber-optic code-division
multiple access channel. In this paper, a combinatorial construction for optimal(15p, 5,1) optical orthogonal codes withp congruent to 1 modulo 4 and greater than 5 is given by applying Weil's Theorem. From this, whenv is a product of primes congruent to 1 modulo 4 and greater than 5, an optimal (15v, 5, 1)-OOC can be obtained by applying
a known recursive construction. 相似文献
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In [ 3 ], a general recursive construction for optical orthogonal codes is presented, that guarantees to approach the optimum asymptotically if the original families are asymptotically optimal. A challenging problem on OOCs is to obtain optimal OOCs, in particular with λ > 1. Recently we developed an algorithmic scheme based on the maximal clique problem (MCP) to search for optimal (n, 4, 2)‐OOCs for orders up to n = 44. In this paper, we concentrate on recursive constructions for optimal (n, 4, 2)‐OOCs. While “most” of the codewords can be constructed by general recursive techniques, there remains a gap in general between this and the optimal OOC. In some cases, this gap can be closed, giving recursive constructions for optimal (n, 4, 2)‐OOCs. This is predicated on reducing a series of recursive constructions for optimal (n, 4, 2)‐OOCs to a single, finite maximal clique problem. By solving these finite MCP problems, we can extend the general recursive construction for OOCs in [ 3 ] to obtain new recursive constructions that give an optimal (n · 2x, 4, 2)‐OOC with x ≥ 3, if there exists a CSQS(n). © 2004 Wiley Periodicals, Inc. 相似文献
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We present several new families of multiple wavelength (2-dimensional) optical orthogonal codes (2D-OOCs) with ideal auto-correlation λa=0 (codes with at most one pulse per wavelength). We also provide a construction which yields multiple weight codes. All of our constructions produce codes that are either optimal with respect to the Johnson bound (J-optimal), or are asymptotically optimal and maximal. The constructions are based on certain pointsets in finite projective spaces of dimension k over GF(q) denoted PG(k,q). 相似文献
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Let(X,Y),(X_1,Y_1),…,(X_n,Y_n)be iid.random vectors,where Y is one-dimensional.It is desired to estimate the conditional median(X)of Y,by use of Z_n={(X_i,Y_i),i=1,…,n}and X.Denote by(X,Z_n)the kNN estimate of(X),and putH_(nk)(Z_n)=E{|(X,Z_n)-(X)||Z_n},the conditional mean absolute error.This articalestablishes the optimal convergence rate of P(H_(nk_n)(Z_n)>ε),under fairly generalassumptions on(X,Y)and k_n,which tends to ∞ in some suitable way. 相似文献
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Ye Cinan 《数学年刊B辑(英文版)》1986,7(3):384-396
Suppose that there is a variance components model
$$\[\left\{ {\begin{array}{*{20}{c}}
{E\mathop Y\limits_{n \times 1} = \mathop X\limits_{n \times p} \mathop \beta \limits_{p \times 1} }\{DY = \sigma _2^2{V_1} + \sigma _2^2{V_2}}
\end{array}} \right.\]$$
where $\[\beta \]$,$\[\sigma _1^2\]$ and $\[\sigma _2^2\]$ are all unknown, $\[X,V > 0\]$ and $\[{V_2} > 0\]$ are all known, $\[r(X) < n\]$. The author estimates simultaneously $\[(\sigma _1^2,\sigma _2^2)\]$. Estimators are restricted to the class $\[D = \{ d({A_1}{A_2}) = ({Y^''}{A_1}Y,{Y^''}{A_2}Y),{A_1} \ge 0,{A_2} \ge 0\} \]$. Suppose that the loss function is $\[L(d({A_1},{A_2}),(\sigma _1^2,\sigma _2^2)) = \frac{1}{{\sigma _1^4}}({Y^''}{A_1}Y - \sigma _1^2) + \frac{1}{{\sigma _2^4}}{({Y^''}{A_2}Y - \sigma _2^2)^2}\]$.
This paper gives a necessary and sufficient condition for $\[d({A_1},{A_2})\]$ to be an equivariant D-asmissible estimator under the restriction $\[{V_1} = {V_2}\]$, and a sufficient condition and a necessary condition for $\[d({A_1},{A_2})\]$ to equivariant D-asmissible without the restriction. 相似文献
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提出并使用如下广义复合隐迭代格式逼近非扩张映像族{Ti}Ni=1公共不动点:{xn=αnxn-1 (1-αn)Tnyn,yn=rnxn snxn-1 tnTnxn wnTnxn-1,rn sn tn wn=1,{αn},{rn},{sn},{tn},{wn}∈[0,1],这里Tn=TnmodN.该文提出的广义复合隐迭代格式包含了目前多种迭代格式,因此,所得强弱收敛定理推广及发展了Mann,Ishikawa,XuandOri,等许多作者的结果. 相似文献
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An improved product construction is presented for rotational Steiner quadruple systems. Direct constructions are also provided for small orders. It is known that the existence of a rotational Steiner quadruple system of order υ+1 implies the existence of an optimal optical orthogonal code of length υ with weight four and index two. New infinite families of orders are also obtained for both rotational Steiner quadruple systems and optimal optical orthogonal codes. © 2002 Wiley Periodicals, Inc. J Combin Designs 10: 433–443, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jcd.10025 相似文献
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于志华 《数学的实践与认识》2014,(6)
长度为n重量为w的避免冲突码C是群Z_n的w元子集族,满足对任意的x,y∈C,x≠y有d*(x)∩d*(y)=Φ,其中d*(x)={a-b(mod n):a,b∈x,a≠b}.避免冲突码适用于无反馈时隙同步多址冲突信道.C中的元素称为码字,C中所包含的码字的个数称为码的容量,它是系统中所支持的潜在用户的个数.利用已有的3种构造方法给出了重量在4到10之间的一些最优CAC(p,w)码类. 相似文献
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We investigate further the existence question regarding optimal (v, 4, 2, 1) optical orthogonal codes begun in Momihara and Buratti (IEEE Trans Inform Theory 55:514–523, 2009). We give some
non-existence results for infinitely many values of v ≡ ± 3 (mod 9) and several explicit constructions for infinite classes of perfect optical orthogonal codes. 相似文献
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Let Ф(u ×v, k, Aa, Ac) be the largest possible number of codewords among all two- dimensional (u ×v, k, λa, λc) optical orthogonal codes. A 2-D (u× v, k, λa, λ)-OOC with Ф(u× v, k, λa, λc) codewords is said to be maximum. In this paper, the number of codewords of a maximum 2-D (u × v, 4, 1, 3)-OOC has been determined. 相似文献